Adjustment of plasma properties in magnetron sputtering by pulsed powering in unipolar/bipolar hybrid pulse mode

A new method of pulsed powering the magnetron discharge using a pulsed switching of the anode has been developed. Practically, this hybrid pulse mode is a combination of the conventional unipolar and bipolar pulsed powering, where the time slices of both pulse modes can be freely adjusted at a time scale smaller than 1 ms, i.e. much shorter than necessary for the deposition of one monolayer. This allows varying the average plasma parameters freely between the typical values of unipolar and bipolar pulse mode. During deposition of piezoelectric AlN, the film stress could be shifted in a wide range by changing the pulse mode ratio. In combination with the other known process parameters, it was possible to shift the film stress between compressive and tensile while maintaining piezoelectric properties. Hence, in addition to classical deposition parameters such as pressure or temperature, this new parameter gives an additional degree of freedom for optimization of film properties independent from sputtering power and deposition rate.